In most deployment scenarios, the limiting factor of the system is network bandwidth. Important factors to consider are the number of messages per second that your system will receive from your data sources, the size (in bytes) of each message, and the number of concurrent client connections you expect.

Tracking Server 9.3.1 and earlier versions come with a Java applet that can connect to Tracking Server and display basic symbology in real time. Later versions will be supported by the ArcGIS APIs for Flex and Microsoft Silverlight.